1. Field of the Invention
The present invention relates to a method for tightening a bolt connection by elongation of the bolt where a power wrench is used and where the strokes of a power element, especially of a hydraulic cylinder, are converted into a rotational movement of a tightening tool. In particular, the power wrench used should be a tool where the angle of rotation transcribed per stroke of the power element forms a constant.
2. Description of the Related Art
In the production of high-strength pre-stressed bolt connections, adjustment of the pre-stressing is often necessary in order to produce a specified elongation of the bolt within a relatively small process-reliable tolerance range.
Bolt elongation may be checked, for example, by continuous ultrasonic measurement in order to ensure the correct elongation of the bolt. In addition, methods are known for tightening bolt connections where the angle of rotation of the bolt is measured by a rotation angle sensor during application of the force while the power wrench is controlled using the values of the rotation angle sensor. However, in this case, conventional power wrenches without such sensors can no longer be used. In addition, these engineering control methods are quite costly.